1. Field of the Invention
The present invention relates to a liquid crystal display device and, more particularly, to a so-called active matrix type of liquid crystal display device.
2. Background Art
An active matrix type of liquid crystal display device includes substrates disposed in opposition to each other with a liquid crystal interposed therebetween, gate signal lines disposed to be extended in the x direction and to be juxtaposed in the y direction, drain signal lines disposed to be extended in the y direction and to be juxtaposed in the x direction, and pixel areas each constituted by an area surrounded by adjacent ones of the gate signal lines and adjacent ones of the drain signal lines on a liquid-crystal-side surface of one of the substrates.
Each of the pixel areas is provided with a switching element which is operated by a scanning signal supplied from one of the adjacent gate signal lines, and a pixel electrode which is supplied with a video signal from one of the adjacent drain signal lines via the switching element.
This pixel electrode controls the optical transmissivity of the liquid crystal by causing an electric field to be generated between the pixel electrode and a counter electrode, and two kinds of constructions are known: the first kind of construction is such that the counter electrode is formed on a liquid-crystal-side surface of the other of the substrates, while the other kind of construction is such that the counter electrode is formed on the liquid-crystal-side surface of the one of the substrates.
An electronic circuit is incorporated in the liquid-crystal-side surface of each of the substrates in the form of a stacked structure of a conductive layer, a semiconductor layer or an insulating layer formed in a predetermined pattern.
Another construction is known in which spacers are formed on the liquid-crystal-side surface of either of the substrates to realize the spacer function of ensuring the gap between the substrates disposed in opposition to each other with the liquid crystal interposed therebetween. This is because as compared with the existing beads or fibers, the spacers can be formed at predetermined positions and the uniformity of the gap between the substrates can be easily ensured.
Driver circuit ICs (driver chips) which supply signals to the gate signal lines or the drain signal lines are mounted on the one of the substrates on which the signal lines are formed. However, in recent year, a mounting method called an FCA (or COG) method has widely been adopted in which the driver chips are directly mounted in a face-down state so that their input bumps and output bumps are connected to interconnection layers (signal lines) on the substrate.
This is because the number of lines to be led to the outside can be reduced even in the case of liquid crystal display devices of higher resolution.
In a general construction for supplying signals and power to the driver chips, supply lines for signals and power are formed on a surface of a printed circuit board disposed close to the substrate, and signals and power are individually supplied to the respective driver chips through the supply lines. However, in recent years, another construction has been known in which at least either signals or power is transmitted without being passed through the printed circuit board for the purpose of a further reduction in cost.